Title :
Mobile satellite CDMA system robust to Doppler shift
Author :
Kajiwara, Akihiro
Author_Institution :
Third Res. Cente, JDA, Tachikawa, Japan
fDate :
8/1/1995 12:00:00 AM
Abstract :
This paper suggests a dual-channel PSK demodulator for LEO satellite DS/CDMA communications, whose performance is absolutely invariant to time-variant Doppler offset of a carrier and local oscillator instability. The demodulator does not require any preamble (pilot signal) for carrier recovery, differential encoder/decoder, and carrier recovery circuit such as PLL and Costas loop, thereby resulting in high transmission efficiency and system complexity reduction. In a CDMA channel with the demodulator, the transmitted CDMA signal is composed of two orthogonal linear polarized components, which are spread by different spreading codes, and only one of which is modulated by the data stream. At the receiver, one of the two components despread by the corresponding matched-filter is utilized as a pilot reference carrier for the demodulation. Thereby, the Doppler offset is completely eliminated from the received signal since both these components exhibit the same Doppler and local oscillator instability
Keywords :
Doppler effect; code division multiple access; matched filters; mobile satellite communication; phase shift keying; pseudonoise codes; spread spectrum communication; DS/CDMA communications; Doppler shift; LEO satellite; carrier recovery; data stream; dual-channel PSK demodulator; local oscillator instability; matched-filter; mobile satellite CDMA system; orthogonal linear polarized components; performance; pilot reference carrier; receiver; spreading codes; system complexity reduction; time-variant Doppler offset; transmission efficiency; Artificial satellites; Decoding; Demodulation; Doppler shift; Local oscillators; Low earth orbit satellites; Mobile communication; Multiaccess communication; Phase shift keying; Robustness;
Journal_Title :
Vehicular Technology, IEEE Transactions on